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Missile Defense

Technology has always found its greatest consumer in a nation's war and defense efforts. Since the last attempts at a "Star Wars" defense system, has technology changed considerably enough to make the latest Missile Defense initiatives more successful? Can such an application of science be successful? Is a militarized space inevitable, necessary or impossible?

Read Debates, a new Web-only feature culled from Readers' Opinions, published every Thursday.

gisterme - 04:15pm Jan 31, 2002 EST (#11149 of 11160)

http://www.3m.com/about3M/technologies/lightmgmt/learn/reflection.jhtml

This is a link to a 3M site that's about reflective polymer films that might be considered decals. These are said to be able to achieve 98% reflectivity at the wavelengths they are designed to reflect.

However there's no data about how much energy they can tolerate while maintaining their reflective properties. So, even if a film like this was reflecting light from a high energy laser, light that was at just the wavelenghth the film was designed for, and the film reflected 98% of the incident energy, it would still have to dissipate 2% of the incident energy without changing its reflective properties.

I believe the energy level we arbitrarily bandied about before when we were talking numbers was 1 kw/cm^2 as a baseline for being able to cut materials. That came from published power levels for industrial lasers. At that level, the the reflective film would have to be able to dissipate 20 Watts (2% of the 1kw) per square centimeter without changing its properties. Not likely for a precisely ordered plastic structure that has microns thick layers. Sorry, Robert. Of course, once the properties of the plastic begin to change due to heating, the reflectivity will go down, energy absorbtion go up and, uh oh, here comes the smoke... :-) The energy dissipation in the glass of a regular 100 Watt light bulb would be far less than 20W/cm^2...that's way too hot to touch. Try putting some saran wrap on a 100W light bulb that's lit, Robert. See what happens.

This 3M reflective film is pretty cool though. I can think of a lot of uses for such a thing. If you're interested, Robert, you can probably get some temperature range specifications for that family of reflective films from 3M. I doubt that they'd have direct per-unit-area energy dissipation numbers, but they might.

rshow55 - 05:03pm Jan 31, 2002 EST (#11150 of 11160)

Thank you for the reference !

But . . . for five seconds . . with good adhesion to a surface that is (for this purpose) a good heat sink ? ? ? ? Is destruction sure? 20 watts for 5 seconds is enough energy to evaporate some water - - but not much . . . let me check this.

If folks worked, they might move from 98% to a higher reflectance, too.

On some other applications, DIRECTLY connected to countermeasures for the mid-course interception system - - the heat dissipation isn't an issue.

And reflectance can be made higher, at least at low energy fluxes. If that 3m coating, tuned to IR, was put on a layer of mylared gold -- for instance on a "decoy balloon" encasing a warhead - - assembly reflectance (at least for low energy fluxes) might well top 99.9% . Precious little IR radiation from such a very "unblack" body.

Also, for such a balloon, with angle of incidence equal to angle of reflection -- return signature, from a radar beam, or a lasar beam, would be very small.

Some reasons, I believe that some excellent engineers and companies, with services that can be well used elsewhere, ought to be redeployed, on a "no fault" basis.

. . .

(More than by the way, there was a line in President Bush's State of the Union adress, about weapons of mass destruction, that I really liked.)

rshow55 - 05:37pm Jan 31, 2002 EST (#11151 of 11160)

MD10997 rshow55 1/23/02 6:35pm indicates that 20 watts/sec for 5 seconds might well destroy the reflectance of a 3m type plastic film by heating -- that is the heat needed to evaporate about a half mm of water. Without heat flow out --- that much heat would be destructive. For such a flux, heat sinking would be critical, and maybe inadequate. (I haven't found data, and done that calculation - but I used to be able to guess fairly well.)

With another decade on reflectance (to 99.8%) heat dissipation, for 5 seconds, wouldn't be a problem, even with heat flow from the film equal to zero.

Again, heat flux wouldn't be an issue for IR "black body" radiation, or for radar or light reflectance, on a decoy balloon shield for a warhead. Such a countermeasure, especially in a group of other balloons less reflective, and therefore easier to see and lock on to - - might be a very effective countermeasure -- among a universe of MANY possible countermeasures.

The BMD tasks are so touchy that countermeasures for them are comparatively very easy. Before, I've estimated that, in dollar terms, countermeasures might be a million times cheaper than the cost of developing the weapons themselves. That still seems reasonable to me. And at that cost ratio, even for a rich country, these "weapons" and "defenses" aren't worth building.

mazza9 - 05:43pm Jan 31, 2002 EST (#11152 of 11160)
Louis Mazza

RShow55:

The 3M link speaks of packaging film and reflective devices for safety purposes. We've all seen runners at dusk because of this film on their sneakers and jogging togs. This type of film has been around for years. I remember attaching this to my bicycle. But that in no ways suggests that this material could be applied to a missile body to defeat a laser beam.

I'm glad you recognize that the ABL laser works. Given the State of the Union assertion that there is an "Axis of Terror" we should proceed. Reminder, 80+ Scud missiles were fired by Saddam. We warned him and had he fired WMD warheads Iraq would still be glowing. We know that the ecological damage of his torching of the Kuwait oil fields demonstrates the mindset we face. Until we deal with these maniacs, the BMD investment is wise.

LouMazza

rshow55 - 05:54pm Jan 31, 2002 EST (#11153 of 11160)

Last sentence includes until . . . and I don't disagree. I've been sending the message, pretty consistently, that approaches to BMD besides the "high tech" ones have to be considered.

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